The present invention relates to a support arrangement of a roll in a fibrous-web machine. The invention generally relates to supporting a bearing of a roll of a fibrous-web machine or an equivalent shaft to the frame structure. Particularly, the invention relates to a roll of a device or a section of a paper or board machine and supporting its bearing to the frame structure when external force applies to the roll. Such external force can be caused e.g. by another roll, a support fabric or a web reel.
The vibration of rolls is a great problem with present-day fibrous-web machines, inter alia, due to the increase in operating speed. Traditionally, the rolls are fastened in the foundation as rigidly as possible, this is particularly the case with the carrier rolls of a slitter-winder.
Specifications WO9849394, WO0004227 and WO0004228 describe arrangements in which in the bearing housing of a roll of a paper machine has been arranged a tunable vibration damper. In the arrangements presented in the specifications, the tuning of the frequency of the vibration being damped has been implemented by changing the position of the mass in the vibrating rod or, alternatively, by changing the volume of the mass. When the access to the damper is relatively easy, the tuning can be changed even during the operation of the machine. In these, the damper is outside the roll, whereby it, inter alia, occupies considerable space. This kind of an arrangement does not always provide good enough damping.
FI patent 94458 describes a method and apparatus for controlling the vibration of the rolls of a paper machine. In the method, the positions of the critical speed ranges of the roll are changed during run. Critical speed is changed by changing the mass and/or the rigidity of the roll and/or the support point of the roll. As a possibility is presented changing the rigidity of the end bearing of the roll. Between the washer of the bearing housings of the end bearings and the frame, intermediate pieces of elastic material can be installed. By adjusting the force with which the bearing housing presses the intermediate pieces against the frame, it is possible to adjust the rigidity of the fastening of the bearing housings. Said pressing force can be adjusted by means of a cylinder device or a screw. A problem of such an arrangement is, however, that simultaneously as the critical speed ranges are changed by making the support elastic, the static rigidity of the support suffers. Particularly in such an arrangement, the static rigidity of the support also weakens in such directions in which it is not desired. This causes problems particularly in targets demanding accurate setting, such are e.g. nip contacts between the rolls and between the roll and the web reel.
Specification JP 3082843 describes an arrangement for minimizing vibrations in a roll. The drive motor of the roll is elastically fastened in the frame. The fastening comprises a rubber intermediate piece enduring vibration between the base plate of the fastening part and the frame. The fastening bolts of the base plate extend through the frame plate into a cylinder fastened on the lower surface of the frame plate in which they are fastened in a piston in the cylinder. Below the fastening bolt heads, there are rubber sleeves, whereby the fastening of the base plate is provided floating. On the inner surface of the cylinder, there is a projection which limits the upward motion of the piston in the cylinder. Between the cylinder ceiling and the upper surface of the piston, there is a spring and, between the lower surface of the piston and the bottom of the cylinder, there is a pressure space in which compressed air is the pressure medium. The piston is run with compressed air first against the projection of the inner surface of the cylinder, whereby minimum pressing force is applied on the rubber intermediate pieces and sleeves. When the pressure of compressed air below the piston is decreased, the piston moves downwards from the force of the spring being above the piston, whereby greater pressing force is applied on the rubber intermediate pieces and rubber sleeves. With the pressure of pressure medium being below the piston, it is then possible to adjust the rigidity of the fastening of the roll. A problem of the arrangement presented in this specification is also that making the support more elastic causes easily that elasticity, particularly its direction, is not sufficiently controlled.